P0420 Code Reappears After Clearing: Possible Faulty Connection or Catalytic Converter Issue in 2000 Model Vehicles?

How long does it typically take for a P0420 code to be set and remain active? Can a loose or faulty electrical connection cause this code to appear intermittently? I recently cleared the P0420 diagnostic trouble code using an OBD2 scanner, and it disappeared. However, after driving approximately 2,000 miles, the same code reappeared. My initial suspicion is not a failing catalytic converter, but rather a faulty or intermittent wiring connection. I'm seeking confirmation on whether such connections can trigger or reset P0420 codes. Technical details: - The P0420 code indicates that the downstream oxygen sensor (HO2S) is not detecting a proper exhaust gas reduction ratio, which suggests inefficient catalytic converter performance or upstream issues. - Possible causes include: - Leaded fuel used where unleaded was required (unlikely in modern vehicles) - Damaged or improperly connected downstream O2 sensor wiring - Faulty engine coolant temperature sensor - Exhaust system leaks (manifold, catalytic converter, muffler, or exhaust pipe) - Failed or underperforming catalytic converter (most likely cause) - Retarded spark timing - Fuel injector leakage or high fuel pressure - Cylinder misfire or oil contamination I am particularly concerned about intermittent wiring connections that may not show symptoms until after long-distance driving. Any insights on how to diagnose this in a 2000 model vehicle would be greatly appreciated.